There is a desire for low cost electrical machines for converting between electrical and mechanical energy that have both high efficiency and high performance capability. Unfortunately, current devices tend to suffer from one or more of a number of deficiencies that include low efficiency, low performance or speed capability, complex and expensive construction and poor heat transfer. One factor contributing to both the losses and complexity of many machines is the required use of laminations. Laminations reduce eddy current losses and the materials can be chosen for low hysteresis losses. However, the lamination losses still tend be about 3-4% or higher, depending on the lamination thickness, material grade and rotor operating speed. Another deficiency in many current designs is the result of slot winding. Slot winding allows for placement and structural support of armature windings while having a small air gap. However, the structure in which these slots are formed undesirably increases the inductance of the armature coils and also causes field variations during rotation, giving rise to added losses.
Other radial gap air core motor-generators have previously been constructed by winding individual coils and inserting them into a mold and potting them with epoxy or other curable resin. Unfortunately, this manufacturing method suffers from deficiencies including high tooling costs and long manufacturing times which make it costly in mass production operations. Yet another inherent difficulty with this construction is that the structural strength of the whole armature is provided by the potting and the adhesive bonding strength between the windings and resin. For some types of winding wires, and those optimized for high voltage operation with an outer serve, the inherent bond strength can be very low. As a result, these conventionally potted air core armatures do not provide adequate strength for operation. Further, the compaction of the windings is less than ideal because the windings must be manually inserted prior to potting into oversized tooling. The required potting operations for air core motor-generators are also generally considered one of the key deficiencies with air core motor-generators.
To eliminate these deficiencies, air core type electrical machines can be created. Unfortunately, current air core electrical machines still suffer from deficiencies that can include, low efficiency, limited operational life, poor heat transfer, and complicated, difficult or costly constructions. A better electrical machine providing high efficiency, high performance with reliable life and low manufacturing cost is needed.